The proposed project aims to develop techniques to quantify trabecular bone density and structure using Magnetic Resonance (MR) techniques. The difference between the magnetic susceptibility of trabecular bone and bone marrow results in a decrease in the marrow relaxation time, T2*, which is proportional to the trabecular density and spatial distribution. This reduction in T2* will be quantified using human bone specimens and related to the surrounding trabecular density measured using quantitative computed tomography (QCT), and to the mechanical strength of the specimens. Image analysis techniques will be developed in order to characterize trabecular pattern in high resolution MR images. The perimeter-to-area ratio, trabecular spacing, and the fractal dimension of the trabecular boundary will be derived along different planes, and trabecular bone anisotropy will be deduced. The con-elation between these measures of structure and mechanical strength of the specimens and histomorphometric estimates of the mean trabecular spacing and dimensions will be derived. After establishing the effectiveness of these techniques, a case control study to determine the efficacy of these outcome variables as predictors of fracture risk will be conducted in postmenopausal women (60-70 years) with and without vertebral fractures. Trabecular bone density of the lumbar spine will be assessed using QCT. T2* will be measured using MR imaging and bone structure will be quantified using the image analysis techniques developed. Logistic regression will be used to determine whether these outcome variables are better predictors of relative fracture risk compared to measures of bone density alone.